The preparation of gas oil is nowadays important in view of the increasing demand for this type of refinery product. It is known to prepare a gas oil fraction and other hydrocarbon fractions such as naphtha, kerosene and wax by combining different refinery product streams and subjecting the combined stream obtained to a fractionating process.
For example, a high quality gas oil fraction can be obtained by combining a product stream obtained by hydrocracking a vacuum gas oil with a product stream that has been obtained by hydrotreating a gas oil, and separating the combined products stream in a fractionating section to obtain a number of hydrocarbon fractions, including the gas oil fraction. The general drawback of such a combined processing of product streams is that the energy efficiency of the fractionating section to be used leaves much room for improvement.
Thus, there is a need to prepare high quality gas oil from combined refinery product streams wherein the above drawback is sufficiently dealt with.